Floating Island Technicalities

so I’m trying to make a floating island but i have one question,

my island is 300 blender units long, should i make the base/dirt below it half the size? how dose the length and width of the base affect the hight of the underground part of the floating island?:spin:

hmm… you mean a bit like this?

http://i.ytimg.com/vi/MhprhH7P6-4/2.jpg

or

http://media.comicvine.com/uploads/0/9496/205929-23408-angel-island_large.jpg

it seems to vary… that first one (Island of the Ancients in Super Smash Bros. Brawl) has a fairly large base, but the second (Angel Island in Sonic) is smaller…

there’s also the “Castle in the Sky” :

http://movie88.net/files/js/xheditor/upload/day_100416/201004160935312005.jpg
seems like it’s mostly roots

another one which kinda looks like the Castle in the Sky

http://wolfestyke.com/Castle_in_the_Sky.jpg

hmm…it really seems to vary depending on the island and artist/style… I can’t seem to think of any other floating islands :frowning: